Extrusion die for forming hollow material

ABSTRACT

An extrusion die for forming a hollow material that extrudes a billet comprising a high-strength alloy having high extrusion force and forms a hollow material including a partition wall, comprises a male-type member that extrudes a billet on a downstream side and forms the inner shape of a material and a female-type member that forms the outer shape of the material, wherein a billet guide hole that guides one part of the billet toward the downstream side is provided to the central area of a mandrel section that constitutes the male-type member, four inner formation pieces are mounted in a fixed manner to positions that face the downstream-side opening of the billet guide hole, and the female-type member is provided with an outer formation die hole that faces all of the outer peripheral surfaces of the inner formation pieces and that forms the outer shape of the hollow material.

TECHNICAL FIELD

The present invention relates to an extrusion die for forming a hollowmaterial and, more specifically, to an extrusion die for forming ahollow material having a partition wall provided in the interior thereofby extruding a high-strength alloy, particularly a high-strengthaluminum alloy such as the so-called 7000 series.

BACKGROUND ART

In general, extrusion processing of an aluminum alloy or the like isbroadly employed nowadays since it can provide highly versatilesectional views and is excellent in acquiring hollow materials formed byextrusion.

That is, products formed by extrusion processing have come to be usedbroadly as strength members of structural materials, mechanicalcomponents, and the like, and demands for extrusion members formed witha high-strength alloy, particularly high-strength aluminum alloys of theso-called 7000 series such as 7075, 7N01, 7003, and the like have beenincreasing. Further, as hollow materials formed by extrusion, not onlythe angular columnar shapes but also those with complicated sectionalviews such as a type in a sectional view with a single lateral partitionwall, a type in a sectional view with two lateral partition walls, andthe like have recently been produced.

As an example of conventional extrusion die for molding hollow materialsof complicated sectional views, known are a metal-made three-dimensionalextrusion material manufacturing method and a manufacturing devicethereof (e.g., see Patent Document 1).

The metal-made three dimensional extrusion material manufacturing methodand the manufacturing device thereof are structured to be able to form athree-dimensional extrusion member in which a hollow part and a solidpart exist in a mixed manner in the lengthwise direction.

Further, also known is a hollow material extrusion die for forming ahollow material having a partition wall (e.g., see Patent Document 2).

This extrusion die is structured to be able to form a hollow materialhaving a laterally-long sectional view with a single partition wall anda hollow material having a sectional view with two partition walls.

Further, also known are an extrusion processing method and a device fora metal-made extrusion material with different lateral sectional viewsin the lengthwise direction (e.g., see Patent Document 3). With theextrusion processing method and the device, it is possible toextrusion-mold aluminum-made extrusion materials having differentlateral sectional views in the lengthwise direction.

Patent Document 1: Japanese Unexamined Patent Publication Hei 4-305312Patent Document 2: Japanese Examined Patent Publication Hei 5-9169Patent Document 3: JP No. 3095916

Incidentally, in a case of forming a hollow material of a complicatedsectional view such as a sectional view with two partition walls byusing a high-strength alloy, particularly 7000 series high-strengthaluminum as a hollow member molding material, a pair of opposing outercircumferential walls and two parallel partition walls are formed. Thosepartition walls are in a straight-line form, so that it is consideredthat billets can flow relatively easily.

However, recently, not only the hollow materials having the sectionalview with two partition walls and the like but also hollow materialshaving still more complicated sectional views such as a hollow materialhaving a sectional view with a cross-like partition walls, a hollowmaterial having a sectional view with a curve-shaped partition wall, andthe like are desired due to the reason for improving the strength of thehollow materials, for example.

In a case of the hollow material having a sectional view with across-like partition wall, the cross-like partition walls forming thesectional view with a cross-like shape intersect with each other at thecenters thereof. Thus, the billet formed with an aluminum alloy that isfed from the upstream side and extruded is not easily flown to thedirection orthogonal to each other from the intersection. This causessuch an issue that the cross-like partition walls having theintersection cannot be formed sufficiently.

Further, even in a case where there is no intersection and in a case ofa hollow material having a complicated curve-shaped partition wall, flowof the billet tends to slow down at the curved part. This causes such anissue that the curve-shaped partition wall cannot be formedsufficiently.

Further, while the manufacturing method and the manufacturing device ofthe metallic three-dimensional extrusion material disclosed in PatentDocument 1 described above are structured to be able to mold thethree-dimensional extrusion material in which the hollow part and thesolid part exist in a mixed manner in the lengthwise direction, it isnot possible with the device disclosed in Patent Document 1 to mold thehollow material having an intersection constituted with partition walls.

Further, while the hollow-type material extrusion die having thepartition walls disclosed in Patent Document 2 can mold the hollowmaterial having a laterally long sectional view with a partition walland the hollow material having a sectional view with two partitionwalls, the intersection is formed with the partition walls as describedabove. Thus, the extruded billet can flow in one direction but cannotflow easily from the intersection in the direction orthogonal to thatdirection. Therefore, it is difficult to mold the hollow material havingthe sectional view with a cross-like form inside therein.

Further, while the extrusion processing method and the device for themetallic extrusion materials having different lateral sectional views inthe lengthwise direction disclosed in Patent Document 3 described abovecan extrusion-mold aluminum-made extrusion materials having differentlateral sectional views in the lengthwise direction, it is not possiblewith the device disclosed in Patent Document 3 to mold a hollow materialhaving an intersection constituted with partition walls.

In order to overcome the above-described issues, it is an object of thepresent invention to provide an extrusion die for forming a hollowmaterial capable of easily forming a hollow material having a partitionwall provided inside thereof through extruding a billet formed with ahigh-strength alloy with a large extrusion processing force,particularly a high-strength aluminum alloy such as the so-called 7000series.

DISCLOSURE OF THE INVENTION

In order to achieve the foregoing object, the extrusion die for forminga hollow material according to the present invention is an extrusion diefor forming a hollow material, which includes: a male-type member whichforms an inner shape of the hollow material while guiding a billetconstituted with an aluminum alloy fed from an upstream side toward adownstream side; and a female-type member which holds the male-typemember with an outer circumferential part and forms an outer shape ofthe hollow material, wherein: the male-type member includes a mandrelsection for forming the inner shape, and a holder section connectedintegrally to an outer circumferential part of the mandrel section via aplurality of bridge sections; a billet guide hole for guiding a part ofthe billet toward the downstream side is provided in a center region ofthe mandrel section; an upstream-side opening area of the billet guidehole is formed larger than a downstream-side opening area; and aplurality of inner formation pieces are fixedly mounted on a downstreamside of the billet guide hole and at positions for forming continuouspartition walls inside the hollow material while keeping a billetflow-in gap space forming a merging space of the billet flowing in fromeach of the bridge sections toward the downstream side.

The extrusion die for forming a hollow material according to the presentinvention is structured in the manner described above, so that a part ofthe billet from the billet guide hole provided in the center region ofthe mandrel section is mixed with the billet flown-in from the bridgesection side and extruded out from the billet flow-in space maintainedtoward the downstream side. The billet extruded out from the billetguide hole is extruded out toward the position of the partition wallpart of the hollow material formed by a plurality of inner formationpieces, so that it can sufficiently reach even into complicatedsectional views such as the intersection of the partition walls, thecurved part of the curve-shaped partition walls, etc. As a result, itbecomes possible to easily form the hollow material having partitionwalls provided therein through extruding out the billet formed with ahigh-strength alloy with a large extrusion processing force,particularly a high-strength aluminum alloy such as the so-called 7000series.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional perspective view showing a main part of afirst embodiment of an extrusion die for forming a hollow materialaccording to the present invention;

FIG. 2 is a plan view showing the entire extrusion die for forming thehollow material according to the first embodiment;

FIG. 3 is a cross sectional view taken along a line III-III of FIG. 2,which is a cross sectional view showing a state where a holder and abridge outer circumferential face are formed integrally by a bridgesection press-fit structure and where a billet guide hole is in atwo-stage structure;

FIG. 4 is a fragmentary sectional arrow view taken along a line IV-IV ofFIG. 3;

FIG. 5 is a sectional perspective view of a male-type member and afemale-type member of the first embodiment, which is the entire view ofFIG. 1;

FIG. 6 is an overall plan view showing the surface of the female-typemember of the first embodiment;

FIG. 7 is a perspective view showing a hollow material having asectional view with a cross-like shape formed by the extrusion die forforming the hollow material according to the first embodiment;

FIG. 8 is a second embodiment of the extrusion die for forming a hollowmaterial according to the present invention, which is a cross sectionalview corresponding to FIG. 3 showing a state where a holder and a bridgeouter circumferential face are formed integrally by a bridge sectionpress-fit structure and where a billet guide hole is in a tapered shape;

FIG. 9 is a sectional perspective view of a male-type member and afemale-type member shown in FIG. 8;

FIG. 10 is an overall plan view showing a third embodiment of theextrusion die for forming a hollow material according to the presentinvention;

FIG. 11 is a cross sectional perspective view taken along a line X1-X1of FIG. 10, which is a cross sectional view showing a state where aholder and a bridge outer circumferential face are formed integrally bya bridge section shrink-fit structure and where a billet guide hole isin a two-stage structure;

FIG. 12 shows a fourth embodiment of the extrusion die for forming ahollow material according to the present invention, which is a crosssectional perspective view showing a state where a holder and a bridgeouter circumferential face are formed integrally by a bridge sectionshrink-fit structure and where a billet guide hole is in a taperedshape;

FIG. 13 shows a fifth embodiment of the extrusion die for forming ahollow material according to the present invention, which is an overallplan view showing a state where a holder and a bridge outercircumferential face are formed integrally by a bridge sectionshrink-fit structure;

FIG. 14 is a cross sectional perspective view taken along a line XIV-XIVof FIG. 13;

FIG. 15 is a fragmentary sectional arrow view taken along a line XV-XVof FIG. 14;

FIG. 16 is a perspective view showing a hollow material having asectional view with a lattice form which is formed by the extrusion diefor forming a hollow material according to the fifth embodiment;

FIG. 17 is an overall plan view showing a sixth embodiment of theextrusion die for forming a hollow material according to the presentinvention;

FIG. 18 is a cross sectional view taken along a line XVIII-XVIII of FIG.17;

FIG. 19 is a fragmentary sectional arrow view taken along a line XIX-XIXof FIG. 18;

FIG. 20 is a perspective view showing a hollow material having asectional view with a lattice form which is formed by the extrusion diefor forming a hollow material according to the sixth embodiment;

FIG. 21 shows a seventh embodiment of the extrusion die for forming ahollow material according to the present invention, which is an overallplan view showing a state where a holder and a bridge outercircumferential face are formed integrally by a bridge sectionshrink-fit structure;

FIG. 22 is a cross sectional perspective view taken along a lineXXII-XXII of FIG. 21;

FIG. 23 is a fragmentary sectional arrow view taken along a lineXXIII-XXIII of FIG. 22;

FIG. 24 is a perspective view showing a hollow material having asectional view with a lattice form constituted with partition walls ofdifferent thicknesses, which is formed by the extrusion die for forminga hollow material according to the seventh embodiment;

FIGS. 25A and 25B show schematic views of hollow materials havingcurve-shaped partition walls formed by utilizing eighth and ninthembodiments of the extrusion die for forming a hollow material accordingto the present invention, in which FIG. 25A is a view showing a hollowmaterial having curve-shaped partition walls formed by the extrusion dieof the eighth embodiment and FIG. 25B is a view showing a hollowmaterial having curve-shaped partition walls formed by the extrusion dieof the eighth embodiment;

FIG. 26 is a schematic view of a hollow material having curve-shapedpartition walls formed by utilizing a tenth embodiment of the extrusiondie for forming a hollow material according to the present invention, inwhich two wave-like curve-shaped partition walls are provided;

FIG. 27 is a cross sectional perspective view showing a modificationexample of the fifth embodiment (FIG. 14) according to the presentinvention; and

FIGS. 28A and 28B show perspective views, in which both FIG. 28A andFIG. 28B show modification examples of a hollow material havingpartition walls with intersections formed by utilizing the extrusion diefor forming a hollow material according to the present invention.

BEST MODES FOR CARRYING OUT THE INVENTION

Hereinafter, a first embodiment of an extrusion die for forming a hollowmaterial (simply referred to as an extrusion die hereinafter) of thepresent invention will be described by referring to FIG. 1 to FIG. 6.

An extrusion die 10 of the first embodiment is for forming a hollowmaterial formed with a high-strength alloy, particularly a high-strengthaluminum alloy that is the so-called 7000 series. Further, among hollowmaterials having complicated sectional views such as curve-shapedpartition walls, partition walls forming an intersection, and the like,the extrusion die 10 forms a hollow material 1 having a sectional viewwith a cross formed with partition walls 1 b and 1 b provided in across-like form having an intersection X inside thereof as shown in FIG.7.

As shown in FIG. 1 and FIG. 3, the extrusion die 10 is constituted byincluding: a male-type member 20 having a mandrel section 23 which formsthe inner shape of the hollow material 1 while guiding a billet B formedwith an aluminum alloy extruded out from the upstream side toward thedownstream side; and a female-type member 30 which holds the male-typemember 20 with the outer circumferential part and forms the outer shapeof the hollow material 1.

The male-type member 20 is constituted by including: the mandrel section23; and a holder section 25 which is integrally connected to the outercircumferential part of the mandrel section 23 via a plurality of bridgesections 24.

The holder section 25 is formed in a disc shape as a whole with aprescribed thickness. On the end face of the upstream side of theextrusion direction thereof, formed is a billet introduction opening 25Bin a disc shape as a whole while being sectioned by each of the bridgesections 24.

As will be described later in details, a billet guide hole 28 forguiding a part of the billet B toward the downstream side is provided inthe center region of the mandrel section 23.

Further, an upstream-side opening area 28A of the billet guide hole 28is formed to be larger than the opening area of a downstream-sideopening 28B.

Further, a plurality of (four in this embodiment) inner formation pieces23B are fixed on the side opposing to the downstream-side opening of thebillet guide hole 28 and at positions for forming partition walls havingan intersection X inside the hollow material 1 while keeping a billetinsertion hole BH1 (a billet flow-in gap space) forming a merging spacewith the flow-in billet B from each of the bridge sections 24 on thedownstream side, i.e., towards the female-type member 30 side. The innerformation pieces 23B are provided to the mandrel section 23 via aconnecting section 23M.

Further, in the female-type member 30, an outer formation die hole 30Bfor forming outer shapes of a plurality of the hollow materials 1 isprovided by opposing to the entire outer circumferential face of thefour inner formation pieces 23.

Hereinafter, each structure will be described in more details.

First, the entire extrusion die 10 will be described by referring toFIGS. 2 and 3.

As shown in FIG. 2, the extrusion die 10 is formed in a disc shape as awhole. Further, as shown in FIG. 3, the extrusion die 10 is constitutedby including the male-type member 20, the female-type member 30, and aback die 70 for holding the female-type member 30.

Further, the billet B is housed within a billet extrusion device 80constituted with a chamber and the like disposed in the upstream side ofthe male-type member 20, and extruded out by the billet extrusion device80.

The male-type member 20, the female-type member 30, and the back die 70are connected integrally.

That is, as shown in FIG. 2 and FIG. 3, after the male-type member 20and the female-type member 30 are placed at the positions by twopositioning pins 71, for example, the male-type member 20, thefemale-type member 30, and the back die 70 are connected and fixed bytwo connection bolts 72, for example.

As shown in details in FIGS. 3 and 5, the male-type member 20 isconstituted by including a spider 22. The spider 22 is constituted byincluding: the mandrel section 23 which forms the inner shape of thehollow material 1; the bridge section 24 which supports the mandrelsection 23 and is projected substantially in an X-letter shape towardouter side from the periphery of the mandrel section 23; and the holdersection 25 which is connected integrally via the bridge section 24.

As shown in FIG. 2, the bridge section 24 is constituted with fourpieces of a first bridge 24 a, a second bridge 24 b, a third bridge 24c, and a fourth bridge 24 d disposed clockwise. Further, the spacesbetween each of the bridges 24 a to 24 d form the billet introducingspaces S.

A top face 23A of the mandrel section 23 is formed in a disc-like flatsurface, and the top faces of the bridges 24 a to 24 d are connected tothe top face 23A. The top faces of the bridges 24 a to 24 d are formedin a downward sloping shape from the top face 23A of the mandrel section23 toward the internal circumferential face of the holder section 25.

Further, the top face 23A of the mandrel section 23 is formed as thesame height with a top end face 25A of the holder section 25 (see FIGS.3 and 5) when the spider 22 and the holder section 25 are assembledintegrally.

As shown in FIGS. 1, 3, and 5, tip external circumferential faces 24A ofthe bridges 24 a to 24 d are formed to be engaged with bridge receivingfaces 26B of a bridge holding section 26 of the holder section 25.

That is, in the holder section 25, provided by corresponding to each ofthe bridges 24 a to 24 d are: bridge presser sections 26A which areformed on the top end of the holder section 25 for pressing the tipupper faces 24B (see FIG. 3) of the bridges 24 a to 24 d; and the bridgereceiving faces 26B which are formed continuously to the bridge pressersections 26A and formed to be substantially equal (preferably a littlewider) with respect to the width of the bridge 24 a and the like.

Further, fixing members 27 in a flat square columnar shape, for example,are knocked into the bridge presser sections 26A so that each of thebridges 24 a to 24 d does not rotate.

As shown in FIG. 5, the fixing members 27 are knocked from the aboveinto knock-in holes for the fixing members 27 opened over the upper-sideparts of the bridge presser sections 26A and the bridges 24 a to 24 dafter precisely positioning each of the bridges 24 a to 24 d and thebridge presser sections 26A.

Further, the engaging faces between the tip outer circumferential faces24A of the bridges 24 a to 24 d and the bridge receiving faces 26B ofthe holder section 25 are formed as sloping faces approaching toward thecenter of the die from the upstream side of the extrusion directiontoward the downstream direction. Thus, moment generated at theapplication point of extrusion by the inner formation pieces 23B to bedescribed later can be decreased, thereby making it possible to increasethe strength of each of the bridges 24 a to 24 d. As a result, breakageof each of the bridges 24 a to 24 d can be prevented.

Note that the tip outer circumferential faces 24A of the bridges 24 a to24 d and the bridge receiving faces 26B of the holder section 25 areintegrated by press fitting by a bridge section press-fit structure M.

As shown in FIG. 1 in details, the bottom ends of the bridge sections 24a to 24 d are located at positions distant from the holder receivingface 30A of the female-type member 30 toward the upper side by aprescribed distance, and formed in a shape connected therefrom to aplurality (four in this embodiment) of the inner formation pieces 23Bfor forming the inner shape of the hollow materials 1 (see FIG. 7) viathe connecting section 23M of the mandrel section 23.

Further, at each bottom end of each of the bridges 24 a to 24 d, atunnel-like billet insertion hole BH is formed with the bottom end ofeach of the bridges 24 a to 24 d at the bottom end part of the bridgereceiving face 26B of the holder section 25 and the holder receivingface 30A of the female-type member 30. As shown with an arrow, thebillet insertion hole BH forms a billet merging space where the billetsB introduced from the billet introduction spaces S for introducing eachbillet B are merged.

Thereby, the billets B are introduced from the billet introduction spaceS for introducing each billet B, merged in the billet insertion hole BH,and extruded out to the downstream side.

As shown in FIGS. 1, 3, and 5, the four inner formation pieces 23B areprovided at the downstream-side end of the flow of the billet B of themandrel section 23.

Each of those inner formation pieces 23B is formed substantially in asquare columnar shape and provided at the end of the mandrel section 23via the connecting section 23M as described above (also see FIG. 4).Further, the four inner formation pieces 23B are projected out towardthe female-type member 30 side and, as shown in FIGS. 4 and 6 indetails, formed to be inserted into the outer formation die hole 30Bformed in the female-type member 30.

The female-type member 30 is formed to oppose to the outercircumferential face of the entire four inner formation pieces 23B andin a size securing a gap L1 of a prescribed size.

Further, each of the inner formation pieces 23B is designed to beinserted into the outer formation die hole 30B of the female-type member30, and the gap L1 in the prescribed size set between the outercircumference of each of the inner formation pieces 23B and the outerformation die hole 30B forms a material outer formation hole 50 (seeFIGS. 1, 3, and 5). Furthermore, as shown in FIG. 3, the outer formationdie hole 30B is formed with a straight-line part in a small size and aclearance hole 30C expanded from the straight-line part toward the outercircumference direction of the female-type member 30.

Each of such inner formation pieces 23B is designed to form each of thefour inside spaces 1S of the hollow material 1 in a sectional view witha cross inside thereof as shown in FIG. 7, and the four inner formationpieces 23B are disposed so that the entire shape thereof formssubstantially a square shape as shown in FIG. 4.

As described above, each of the inner formation pieces 23B is providedat the end on the downstream side of the extrusion direction of thematerial inner forming section 23 via the connecting section 23M.

As shown in FIG. 1, on the upstream side of the extrusion direction ofeach of the inner formation pieces 23B, a band-like flange section 23Fprojected toward the outer side from the respective outer circumferencesis provided by being wrapped around the outer circumference of each ofthe inner formation pieces 23B.

As shown in FIGS. 1 and 4, a gap L2 in a prescribed size is formedbetween the opposing flange sections 23F of the inner formation pieces23B that are neighboring to each other. Further, with those gaps L2, thematerial formation inner hole 51 for forming the cross-like partitionwalls 1 b and 1 b of the hollow material 1 is constituted.

Further, the outer circumference of each of the flange sections 23F ofthe inner formation pieces 23B is disposed to oppose to the outerformation die hole 30B formed in the female-type member 30. Further, thegap L1 in the prescribed size is formed between the both, and thematerial formation outer hole 50 for forming outer circumferential walls2 a and 2 a of the hollow material 1 is formed with those gaps L1.

As shown in FIGS. 1, 3, and the like, the top faces of the flangesections 23F of the respective inner formation pieces 23B are on thesame flat surface as that of the holder receiving face 30A of thefemale-type member 30. Thus, the billet B is also extruded out along thetop end faces of the flange sections 23F via the side face of theconnecting section 23M of the mandrel section 23 from the billetinsertion hole BH.

As described above, in the hollow material 1, the single intersection Xis formed with the two partition walls 1 b and 1 b. Thus, the billets Bextruded out only from the billet introduction space S for introducingthe billet B, the billet insertion hole BH, and the billet insertionhole BH1 may not be sufficient to fill up to the intersection X.

Thus, as shown in FIGS. 1 to 4, the die 10 of the first embodiment isstructured to include the billet guide hole 28 which guides a part ofthe billet B toward the downstream side provided in the center region ofthe mandrel section 23.

The billet guide hole 28 is provided by corresponding to theintersection X of the partition walls 1 b and 1 b. Further, the upstreamside opening area located on the billet B flow-in side of the mandrelsection 23 is formed larger than the opening area of the downstream sideopening located on the billet B flow-out side.

Further, on the side opposing to the downstream-side opening of thebillet guide hole 28 and also between the opposing surfaces of theconnecting section 23M, the billet insertion hole BH1 constituting thebillet introduction gap space is provided. The billet insertion hole BH1is for constituting the billet merging space where the billets Bintroduced into the billet introduction spaces S for introducing thebillets B are merged with each other, and the billets B introduced fromthe billet guide hole 28 are extruded out via the billet insertion holeBH1.

That is, as shown in details in FIGS. 1, 3, and 5, the billet guide hole28 of the first embodiment is constituted with a large opening hole 28Aformed with a diameter φ1 on the upstream side including a step part inthe midway of the mandrel section 23 and a small opening hole 28B formedwith a diameter φ2 which introduces a part of the billet B on the lowerside of the mandrel section 23, i.e., on the side of the intersection Xof the partition walls 1 b and 1 b.

Thus, a part of the billet B fed from the upstream side and extruded outis securely introduced into the small opening hole 28B by being guidedby the large opening hole 28A.

Further, since the small opening hole 28B is provided on the lower sideof the mandrel section 23, it is possible to secure thickness of thesmall opening hole 28B to be large in the mandrel section 23. Therefore,the strength of the die for the stress at the time of extrusion can beincreased. As a result, cracking of the die can be prevented.

The region where one corner each of flange sections 23F of the fourinner formation pieces 23B gathers, the position of the intersectionpoint P corresponds to the intersection X formed with the partitionwalls. Further, the position of the small opening hole 28B is set sothat the position of the intersection point P and the center of thesmall opening hole 28B of the billet guide hole 28 to be described laterin details become consistent.

Next, a forming method of the hollow material 1 by the extrusion die 10in the above-described structure will be described.

When the billet B is fed and extruded out by the billet extrusion device80 provided on the upstream side of the extrusion direction of thebillet B for the male-type member 20, the billet B is first introducedinto the billet introduction space S for introducing the billet Bconstituted with the gap formed in the mandrel section 23 of themale-type member 20, the bridge section 24, and the holder section 25,and a part thereof is introduced into the larger opening hole 28A of thebillet guide hole 28.

The billet B introduced into the billet introduction space S isintroduced into the material formation outer hole 50 from the side facesof the first to fourth bridges 24 a to 24 d, the side face of thematerial inner formation section 23, the billet insertion hole BH, thebillet insertion hole BH1, and the top face of the flange section 23F ofeach of the inner formation pieces 23B, and extruded out from thematerial formation outer hole 50.

Meanwhile, a part of the billet B introduced into the large opening hole28A of the billet guide hole 28 is securely introduced into the smallopening hole 28B by being guided by the large opening hole 28A. At thattime, the billet B from the billet insertion hole BH1 is also merged andextruded out.

Then, the extruded and molded hollow material 1 is fed out from amaterial feed-out hole 70A formed in the back die 70. Thereafter, it isheld by a holding mechanism, not shown, and conveyed into a prescribedstockyard or the like.

Next, the hollow material 1 molded by the above-described extrusion die10 according to the above-described first embodiment will be describedby referring to FIG. 7.

The hollow material 1 is constituted with the outer circumferentialwalls 1 a, 1 a having a square sectional view and the partition walls 1b, 1 b in a cross-like form provided inside the outer circumferentialwalls 1 a, 1 a. The center part where the partition walls 1 b and 1 bintersect with each other is the intersection X. Thus, the hollowmaterial 1 is formed in a sectional view with a cross having four spaces1S inside thereof.

The hollow material 1 having such sectional view with a cross is moldedby continuously extruding out the billet B from the material formationouter hole 50 and the material formation inner hole 51 of the extrusiondie 10.

The extrusion die 10 of the first embodiment is structured in the mannerdescribed above, so that following effects can be acquired:

(1) A part of the billet B fed from the upstream side is extruded outfrom the billet guide hole 28 provided in the center region of themandrel section 23 toward the intersection point P where the one cornereach of the flange sections 23F of the four inner formation pieces 23Bgathers. The position of the intersection point P corresponds to theintersection X formed by the partition walls and, further, theintersection point P and the center of the small opening hole 28B of thebillet guide hole 28 are consistent with each other on the same line, sothat the billet B fed through the small opening hole 28B is extruded outvia the intersection point P. Thus, the intersection X can be moldedeasily. As a result, it becomes possible to easily mold the hollowmaterial in which complicated-shape partition walls are provided throughextruding out a billet formed with a high-strength alloy of a highextrusion processing force, particularly a high-strength aluminum alloysuch as the so-called 7000 series.

(2) The Billet guide hole 28 is in a two-stage structure constitutedwith the large opening hole 28A formed on the upper side of the mandrelsection 23 and the small opening hole 28B formed in the lower side ofthe mandrel section 23. A part of the billet B extruded out from theupstream side is securely introduced into the small opening hole 28B bybeing guided by the large opening hole 28A. This makes it possible tosecure the sufficient billet for forming the partition walls.

(3) The engaging face between the tip outer circumferential face 24A ofthe first to fourth bridges 24 a to 24 d of the bridge section 24 andthe bridge receiving face 26B of the bridge holding section 26 is formedas a sloping surface approaching the center of the die toward thedownstream side of the extrusion direction. Therefore, the distancebetween the base end of the bridge receiving face 26B of the holdersection 25 to the application point in the direction orthogonal to theextrusion direction at the inner formation piece 23 from the base endcan be made shorter. Thus, the moment generated at the application pointof the inner formation piece 23 can be decreased, so that the strengthof the first to fourth bridges 24 a to 24 d can be increased. This makesit possible to prevent breakage of the first to fourth bridges 24 a to24 d. As a result, it becomes possible to perform high-speed extrusionand to extend the life of the die even when extrusion-molding the billetB formed with a high-strength alloy of a high extrusion processingforce, particularly a high-strength aluminum alloy such as the so-called7000 series.

(4) Each of the bridges 24 a to 24 d and the bridge receiving face 26Bare formed integrally by the bridge section press-fit structure M, sothat the strength of each of the bridges 24 a to 24 d and in its turnthe strength of the mandrel section 23 can be secured. Thus, thepressure at the time of extrusion of the billet B can be received by theentire male-type member 20. As a result, it becomes possible to performhigh-speed extrusion and to extend the life of the die even whenextrusion-molding the billet B formed with a high-strength alloy of ahigh extrusion processing force, particularly a high-strength aluminumalloy such as the so-called 7000 series.

(5) Each of the bridges 24 a to 24 d and the bridge presser section 26Ais fixed by the whirl-stop fixing members 27 knocked into the knock-inholes opened over the spaces therebetween, so that rotation of each ofthe bridges 24 a to 24 d can be prevented. Thereby, the hollow materials1 of high precision can be molded.

Next, a second embodiment of the extrusion die of the present inventionwill be described by referring to FIG. 8 and FIG. 9.

The shape of the billet guide hole 28 of the extrusion die 10 accordingto the first embodiment is in a two-stage structure of the large openinghole 28A and the small opening hole 28B, whereas it is formed as abillet guide hole 38 in a tapered shape in an extrusion die 11 of thesecond embodiment. However, other members, structures, and the like arecompletely the same as those of the extrusion die 10 of the firstembodiment.

Therefore, the same reference numerals are applied to the samestructures and the same members as those of the first embodiment, andonly the different points will be described. Note here that the mandrelsection 23 is different only in terms of the shapes of the billet guideholes 28 and 38, so that the reference numeral 23 that is the same asthe case of the first embodiment is also applied in the secondembodiment for explanation.

The shape of the billet guide hole 38 of the extrusion die 11 accordingto the second embodiment is formed in a tapered shape which becomessmaller toward the downstream-side opening side from the upstream-sideopening of the mandrel section 23.

Note here that the diameter φ1 of the upstream-side opening of themandrel section 38 is substantially equivalent to the diameter φ1 of thelarge opening hole 28A of the first embodiment, and the diameter φ2 ofthe downstream-side opening of the tapered-shape hole is substantiallyequivalent to the diameter φ2 of the small opening hole 28B of the firstembodiment.

With the billet guide hole 38 of the extrusion die 11 according to thesecond embodiment, as in the case of the first embodiment, in the regionwhere one corner each of flange sections 23F of the four inner formationpieces 23B gathers, the position of the intersection point correspondsto the intersection X formed with the partition walls. Further, theposition of the billet guide hole 38 is set so that the position of theintersection point and the center of the of the billet guide hole 38become consistent with each other.

As in the case of the extrusion die 10 of the first embodiment, it ispossible with the extrusion die 11 of the second embodiment describedabove to mold the hollow material 1 having a sectional view with a crossinside thereof as shown in FIG. 7.

With the extrusion die 11 of the second embodiment described above, itis possible to acquire substantially the same actions as those of theextrusion die 10 of the first embodiment and substantially the sameeffects as those described in (1) to (5). In addition, it is possible toachieve the following effect:

(6) The flow of the billet B can become smooth since the billet guidehole 38 is formed in a tapered shape which becomes smaller from theupstream-side opening of the mandrel section 23 toward thedownstream-side opening side.

Next, a third embodiment of the extrusion die according to the presentinvention will be described by referring to FIG. 10 and FIG. 11.

In the extrusion dice 10 and 11 of the first and second embodiments, thelower part of the first to fourth bridges 24 a to 24 d of the bridgesection 24 and the lower part of the bridge receiving face 26B aresloping in the direction approaching the dice center side as goingtoward the female-type member 30, and those are engaged by the bridgesection press-fit structure M.

In the meantime, in an extrusion die 12 of the third embodiment, a tipouter circumferential face 34A of first to fourth bridges 34 a to 34 dof a bridge section 34 for supporting a mandrel section 33 and a part ofa holder section 125 for holding each of the bridges 34 a to 34 d areformed as an integrated structure by the bridge section shrink-fitstructure N.

Note here that shrink fitting is a method for acquiring strong bondingby utilizing heat, which is a method with which a member such as a discwith a hole is thermally expanded, a shaft formed slightly larger thanthe diameter of the hole is fitted therein, and it is cooled thereafterto be fixed. The method is used as bonding of fastening type. Further,the both (the disc and the shaft in the above case) are tightly fixed byshrink fitting.

A male-type member 120 of the extrusion die 12 according to the thirdembodiment is substantially the same in terms of the entire shape asthose of the extrusion dice 10 and 11 of the first and secondembodiments, and the only difference is that there is no bridge pressersection 26A that is formed in the extrusion die 10 and the like.

A spider 32 of the third embodiment is constituted with: the mandrelsection 33 corresponding to the inner shape of the hollow material 1;and the bridge section 34 which supports the mandrel section 33 andsupports the mandrel section 33.

The bridge section 34 is constituted with a plurality of, i.e., fourbridges of the first bridge 34 a, the second bridge 34 b, the thirdbridge 34 c, and the fourth bridge 34 d projected substantially in anX-letter shape from the periphery of the mandrel section 33 to the outerside, and the space between each of the bridges 34 a to 34 d forms thebillet introduction space S.

In the center region of the mandrel section 33, the billet guide hole 28for guiding a part of the billet B toward the downstream side isprovided. The billet guide hole 28 is formed by corresponding to theintersection X of the partition walls 1 b and 1 b. Further, the billetguide hole 28 is constituted with the large opening hole 28A and thesmall opening hole 28B.

The billet guide hole 28 is in a similar structure as that of the billetguide hole 28 of the extrusion die 10 according to the first embodiment.

A supporting member 36 that is a bridge section supporting mechanism forsupporting each of the bridges 34 a to 34 d is interposed between thelower end of the outer circumference of each of the bridges 34 a to 34 dand the holder receiving face 30A of the female-type member 30. The bothends of the supporting member 36 are fixed over the lower end of each ofthe bridges 34 a to 34 d and the holder receiving face 30A of thefemale-type member 30.

Therefore, a gap of the height of the supporting member 36 is to beformed between the lower end of each of the bridges 34 a to 34 d and theholder section receiving face 30A of the female-type member 30. This gapforms the tunnel-like billet insertion hole BH where the billets Bintroduced within the neighboring bridge insertion holes BH are mergedwith each other. The billet insertion hole BH has the same function asthat of the billet insertion hole BH of the first embodiment, whichconstitutes the billet merging space and the billet flow-in gap space.

Further, four inner formation pieces 33B substantially in the same shapeas that of the inner formation piece 23B are provided in thedownstream-side end of the flow of the billet B of the mandrel section33, and respective flange sections 33F are provided to those innerformation pieces 33B.

Each of the inner formation pieces 33B is projected toward thefemale-type member 30 side and inserted into the outer formation diehole 30B formed in the female-type member 30.

Such inner formation pieces 33B form each of the four inside spaces 1Sof the hollow material 1 having a sectional view with a cross insidethereof as shown in FIG. 7. Further, those inner formation pieces 33Bare formed in a square shape substantially in the same shape as that ofthe inner formation pieces 23B of the first and second embodiments andalso disposed in a square form.

With the extrusion die 12 of the third embodiment described above, it ispossible to mold the hollow material 1 having the sectional view with across inside thereof as shown in FIG. 7.

With the extrusion die 12 of the third embodiment described above, it ispossible to acquire substantially the same actions as those of theextrusion die 10 of the first embodiment and substantially the sameeffects as those described in (1), (2), and (6). In addition, it ispossible to achieve the following effect:

(7) The tip outer circumferential face 34A of each of the bridges 34 ato 34 d and a part of the inner circumferential face of the holdersection 125 are formed integrally by the bridge section shrink-fitstructure N, so that the strength of each of the bridges 34 a to 34 dand in its turn the strength of the mandrel section 33 can be secured.Thus, the pressure at the time of extrusion of the billet B can bereceived by the entire male-type member 20. As a result, it becomespossible to perform high-speed extrusion and to extend the life of thedie even when extrusion-molding the billet B formed with a high-strengthalloy of a high extrusion processing force, particularly a high-strengthaluminum alloy such as the so-called 7000 series.

(8) At the lower end of each of the bridges 34 a to 34 d, the supportingmember 36 is fixed over the lower end of each of those and the holderreceiving face 30A of the female-type member 30, so that a gap of theheight of the supporting member 36 is to be formed between the lower endof each of the bridges 34 a to 34 d and the holder section receivingface 30A of the female-type member 30. The supporting member 36 can formthe tunnel-like billet insertion hole BH where the billets B introducedinto the neighboring bridge insertion spaces S merge with each other andalso can support each of the bridges 34 a to 34 d. Therefore, thesupporting member 36 can serve two roles, so that it is possible toeffectively utilize the member.

Next, a fourth embodiment of the extrusion die according to the presentinvention will be described by referring to FIG. 12.

In an extrusion die 13 of the fourth embodiment, the shape of the billetguide hole 38 is formed different from that of the billet guide hole 28of the extrusion die 12 of the third embodiment. Further, the shape ofthe billet guide hole 38 is the same as that of the billet guide hole 38of the extrusion die 11 of the second embodiment.

Other members, structures, and the like are completely the same as thoseof the extrusion die 12 of the third embodiment. Therefore, the samereference numerals are applied to the same structures and the samemembers as those of the third embodiment, and only the different pointswill be described.

The shape of the billet guide hole 38 of the extrusion die 13 accordingto the fourth embodiment is formed in a tapered shape which becomessmaller toward the downstream-side opening from the upstream-sideopening of the mandrel section 33.

In the extrusion die 13 of the fourth embodiment, the four innerformation pieces 33B are disposed in a square form, so that it ispossible to mold the hollow material 1 having the sectional view with across inside thereof as shown in FIG. 7.

With the extrusion die 13 of the fourth embodiment described above, itis possible to acquire substantially the same actions as those of theextrusion die 12 of the third embodiment and substantially the sameeffects as those described in (1), (2), (7), and (8).

Next, a fifth embodiment of the extrusion die according to the presentinvention will be described by referring to FIG. 13 to FIG. 16.

As in the cases of the third and fourth embodiments, in an extrusion die14 of the fifth embodiment, a tip outer circumferential face 44A of eachof first to fourth bridges 44 a to 44 d and a part of the innercircumferential face of the holder section 125 are fixed integrally bythe bridge section shrink-fit structure N. Thus, the strength of each ofthe bridges 44 a to 44 d and a mandrel section 43 is secured.

In the extrusion die 14, the structure of a billet guide hole 48 isdesigned to be different from those of the billet guide holes 28, 38 ofthe extrusion dice 12, 13 to the third and fourth embodiments. However,other members, structures, and the like are completely the same as thoseof the extrusion dice 13 and 14 of the third and fourth embodiments.

Therefore, the same reference numerals are applied to the samestructures and the same members as those of the third embodiment, andonly the different points will be described.

The extrusion die 14 of the fifth embodiment is structured to be able tomold a hollow material 2 having a sectional view with a lattice formhaving four intersections X as shown in FIG. 16.

The male-type member 120 includes a spider 42 which is constituted with:the mandrel section 43 for molding the inner shape of the hollowmaterial 2; and a bridge section 44 which supports the mandrel section43 and is projected substantially in an X-letter form toward the outerside from the periphery of the mandrel section 43. The spider 42 isintegrally connected with the holder section 125 via the bridge section44.

In FIG. 13, the bridge section 44 is constituted with four bridgesdisposed clockwise, which are a first bridge 44 a, a second bridge 44 b,a third bridge 44 c, and a fourth bridge 44 d. Further, spaces betweeneach of the bridges 44 a to 44 d form the billet introduction spaces Sfor introducing the billet B.

As shown in FIGS. 13 and 14, the billet guide hole 48 is in a two-stagestructure constituted with a large opening hole 48A formed on theupstream side of the mandrel section 43 and a small opening hole 48Bformed in the downstream side of the mandrel section 43, i.e., formed tocorrespond to the position where the intersection X of the partitionwalls 1 b and 1 b of the hollow material 2 can be formed.

The large opening hole 48A is substantially in a square shape on a planview and is formed in a recessed shape that is recessed by a prescribedsize into the lower-part side of the mandrel section 43. A plurality(four in this embodiment) of the small opening holes 48B are formed atthe large opening hole 48A. The large opening hole 48A is provided byopening the holes toward the downstream side of the mandrel section 43from the bottom face of the large opening hole 48A.

In the extrusion die 14 of the fifth embodiment, nine inner formationpieces 43B are provided to be able to correspond to four intersectionsX. Those inner formation pieces 43B are formed substantially in the samesquare shape as that of the inner formation pieces 23B of the extrusiondie 10 of the first embodiment, and are provided in the lower part ofthe mandrel 43 via a connecting section that is in the same structure asthat of the connecting section 23.

Further, those inner formation pieces 43B are disposed to form a squareshape as a whole as shown in FIG. 15. Furthermore, the materialformation inner hole 51 is formed by the gaps L2 between each of theinner formation pieces 43B. Further, the nine inner formation pieces 43Bare inserted into an outer formation die hole 130B of the female-typemember 130.

In the extrusion die 14 of the fifth embodiment, the mandrel 43 issubstantially in the same size as that of the mandrel sections 33 and 33of the extrusion die 13 of the fourth embodiment, and the nine innerformation pieces 43B are provided in the mandrel section 43. Thus, thesize of each of the inner formation pieces 43B is formed to be smallerthan the size of each of the four inner formation pieces 33B of theextrusion die 13 of the fourth embodiment. The mandrel 43 may be formedlarger in a case where each of the inner formation pieces 43B is to beformed larger.

Further, the four regions where one corner each of flange sections 43Fof the nine inner formation pieces 43B gathers, the positions of each ofthe intersection points P correspond to the intersections X formed withthe partition walls. Further, the positions of the small opening holes48B are set so that the positions of the four intersection points P andthe centers of each of the small opening holes 48B of the four billetguide holes 48 become consistent with each other.

Next, the hollow material 2 molded by the extrusion die 14 of theabove-described fifth embodiment will be described by referring to FIG.16.

The hollow material 2 is formed substantially in a square sectionalshape and constituted with two pairs of outer circumferential walls 2 a,2 a disposed to oppose to each other and two each of partition walls 2b, 2 b provided laterally and vertically inside thereof. The sectionalview thereof is a lattice form having nine spaces 2S inside thereof.Further, there are four intersections X where the partition walls 2 band 2 b intersect.

Note that the thickness of the partition walls 2 b and 2 b is the same.

With the extrusion die 14 of the fifth embodiment described above, it ispossible to acquire substantially the same actions as those of theextrusion dice of the third and fourth embodiments and substantially thesame effects as those described in (1), (2), (7), and (8). In addition,it is possible to achieve the following effect:

(9) A part of the billet B fed from the upstream side is extruded outfrom the large opening hole 48A of the billet guide hole 48 provided inthe center region of the mandrel section 43 via the small opening hole48B toward the four intersection points P where the one corner each ofthe flange sections 43F of the nine inner formation pieces 43B gathers.The positions of each of the intersection points P correspond to thefour intersections X formed by the partition walls and, further, each ofthe intersection points P and the centers of the small opening holes 48Bof each of the billet guide holes 48 are consistent with each other onthe same line, so that the billet B fed through each of the smallopening holes 48B is extruded out via each of the intersection points P.Thus, the four intersections X can be molded easily.

Next, a sixth embodiment of the extrusion die according to the presentinvention will be described by referring to FIGS. 17 to 20.

In the extrusion die 14 of the fifth embodiment, there are the foursmall opening holes 48B provided in the bottom face of the large openinghole 48A. However, in an extrusion die 15 of the sixth embodiment, ninesmall opening holes 58B are provided in the bottom face of a largeopening hole 58A.

As described above, the extrusion die 15 of the sixth embodiment isdifferent from the extrusion die 14 of the fifth embodiment only interms of the shapes of the billet guide holes 48B and 58B. Othermembers, structures, and the like are completely the same as those ofthe extrusion die 14 of the fifth embodiment. Therefore, the samereference numerals are applied to the same structures and the samemembers as those of the fifth embodiment, and only the different pointswill be described.

The extrusion die 15 of the sixth embodiment is structured to be able toform a hollow material 3 having a sectional view with a lattice form asshown in FIG. 20. Further, in the hollow material 3, nine intersectionsX are provided.

The male-type member 120 of the extrusion die 15 includes a spider 52which is constituted with: a mandrel section 53 for molding the innershape of the hollow material 2; and a bridge section 54 which supportsthe mandrel section 53 and is projected substantially in an X-letterform toward the outer side from the periphery of the mandrel section 53.The spider 52 is integrally connected with the holder section 125 viathe bridge section 54.

Further, a tip outer circumferential face 54A of each of first to fourthbridges 54 a to 54 d and a part of the inner circumferential face of theholder section 125 are fixed integrally by the bridge section shrink-fitstructure N. Thus, the strength of each of the bridges 54 a to 54 d andthe mandrel section 53 is secured.

In FIG. 17, the bridge section 54 is constituted with four bridgesdisposed clockwise, which are the first bridge 54 a, the second bridge54 b, the third bridge 54 c, and the fourth bridge 54 d. Further, spacesbetween each of the bridges 54 a to 54 d form the billet introductionspaces S for introducing the billet B.

As shown in FIGS. 18 and 19, the billet guide hole 58 is constitutedwith a large opening hole 58A formed on the upstream side of the mandrelsection 53 and a small opening hole 58B formed in the downstream side ofthe mandrel section 53, i.e., formed to correspond to the positionswhere the intersections X of the partition walls 1 b and 1 b.

The large opening hole 58A is substantially in the same shape as that ofthe large opening hole 48A of the extrusion die 14 of the fifthembodiment. That is, the large opening hole 58A is formed substantiallyin a square shape on a plan view and is formed in a recessed shape thatis recessed by a prescribed size into the lower-part side of the mandrelsection 53. The small opening holes 58B are formed in the bottom face ofthe large opening hole 58 a. Nine small opening holes 58B are providedby opening the holes toward the downstream side of the mandrel section53 from the bottom face of the large opening hole 58A.

Further, those small opening holes 58B are designed to correspond to thenine intersections X for forming the hollow material 3 having thesectional view with a lattice, and sixteen inner formation pieces 53Bare provided in the lower part of the mandrel 53 to be able to form theintersections X. In the nine regions where one corner each of flangesections 53F of the sixteen inner formation pieces 53B gathers, thepositions of each of the intersection points P correspond to theintersections X. Further, the positions of the small opening holes 58Bare set so that the positions of the nine intersection points P and thecenters of each of the small opening holes 58B of the nine billet guideholes 58 become consistent with each other.

There are the nine small opening holes 58B provided in the bottom faceof the large opening hole 58A, so that the plan shape of the largeopening hole 58A is formed larger than that of the large opening hole48A of the fifth embodiment. Further, the size of each of the innerformation pieces 53B is substantially the same as the size of each ofthe inner formation pieces 43B of the extrusion die 14 of the fifthembodiment, so that the size of the mandrel 53 of the extrusion die 15is formed larger than the size of the mandrel 43 of the extrusion die 14of the fifth embodiment.

Therefore, the size of the outer formation die hole 130B of the femaletype 130 for housing the sixteen inner formation pieces 53B is formedlarger than the size of the outer formation die hole 30B of theextrusion die 14 of the fifth embodiment.

Further, each of the sixteen inner formation pieces 53B is in the samesquare shape and disposed to form a square shape as a whole as shown inFIG. 19. Furthermore, the material formation inner hole 51 is formed bythe gaps L2 between each of the inner formation pieces 53B. Further, thesixteen inner formation pieces 53B disposed in a square shape areinserted into the outer formation die hole 130B of the female-typemember 130.

Next, the hollow material 3 molded by the extrusion die 16 of theabove-described sixth embodiment will be described by referring to FIG.20.

The hollow material 3 is formed substantially in a square sectionalshape and constituted with two pairs of outer circumferential walls 3 a,3 a disposed to oppose to each other and three each of partition walls 3b, 3 b provided laterally and vertically inside thereof. The sectionalview thereof is a lattice form having sixteen spaces 3S inside thereof.Further, there are nine intersections X where the partition walls 3 band 3 b intersect.

The three each of the partition walls 3 b and 3 b provided laterally andvertically are formed in the same thickness.

With the extrusion die 15 of the sixth embodiment described above, it isalso possible to acquire substantially the same actions as those of theextrusion die 14 of the fifth embodiment and substantially the sameeffects as those described in (1), (2), (7), and (8). In addition, it ispossible to achieve the following effect:

(10) A part of the billet B fed from the upstream side is extruded outfrom the large opening hole 58A of the billet guide hole 58 provided inthe center region of the mandrel section 53 via the small opening holes58B toward the nine intersection points P where the one corner each ofthe flange sections 53F of the sixteen inner formation pieces 53Bgathers. The positions of each of the intersection points P correspondto the nine intersections X formed by the partition walls and, further,each of the intersection points P and the centers of the small openingholes 58B of each of the billet guide holes 58 are consistent with eachother on the same line, so that the billet B fed through each of thesmall opening holes 58B is extruded out via each of the intersectionpoints R Thus, the hollow material 3 with the lattice-form sectionalview having the nine intersections X can be molded easily.

Next, a seventh embodiment of the extrusion die according to the presentinvention will be described by referring to FIGS. 21 to 24.

In an extrusion die 16 of the seventh embodiment, the structure of abillet guide hole 68 is formed different from that of the billet guidehole 58 of the extrusion die 15 of the sixth embodiment. However, othermembers, structures, and the like are completely the same as those ofthe extrusion die 15 of the sixth embodiment. Therefore, the samereference numerals are applied to the same structures and the samemembers as those of the sixth embodiment, and only the different pointswill be described.

The male-type member 120 of the extrusion die 16 includes a spider 62which is constituted with: a mandrel section 63 for molding the innershape of the hollow material 3; and a bridge section 64 which supportsthe mandrel section 63 and is projected substantially in an X-letterform toward the outer side from the periphery of the mandrel section 63.The spider 62 is integrally connected with the holder section 125 viathe bridge section 64.

Further, a tip outer circumferential face 64A of each of bridges 64 a to64 d and a part of the inner circumferential face of the holder section125 are fixed integrally by the bridge section shrink-fit structure N.Thus, the strength of each of the bridges 64 a to 64 d and the mandrelsection 63 is secured.

In FIG. 21, the bridge section 64 is constituted with four bridgesdisposed clockwise, which are the first bridge 64 a, the second bridge64 b, the third bridge 64 c, and the fourth bridge 64 d. Further, spacesbetween each of the bridges 64 a to 64 d form the billet introductionspaces S.

The extrusion die 16 of the seventh embodiment is structured to be ableto form a hollow material 4 having a sectional view with a lattice formas shown in FIG. 24. Further, in the hollow material 4, there are nineintersections X that are formed by partition walls of differentthicknesses. The billet guide hole 68 is structured to be able tocorrespond to those intersections X.

That is, the billet guide hole 68 is constituted with a large openinghole 68A provided on the upper side of the mandrel section 63 and ninesmall opening holes 68B formed in the lower side of the mandrel section63 by corresponding to each of the nine intersections X. The largeopening hole 68A is substantially in the same shape as that of the largeopening hole 58A of the billet guide hole 58 of the extrusion die 15 ofthe sixth embodiment.

Further, the small opening holes 68B are formed by opening the holesfrom the bottom face of the large opening hole 68A toward theintersection X side, i.e., toward the female-type member 130 side.

The small opening holes 68B are constituted with three kinds havingdifferent opening areas as shown in FIGS. 21 and 23.

That is, among three each of the small opening holes 68B disposedlaterally and vertically in an equivalent manner, a single first smallopening hole 68B1 of a largest opening area is disposed in the center,and second small opening holes 68B2 of a second largest opening area areprovided on cross-like lines with respect to the first small openinghole 68B1 on both sides thereof.

Further, on lines in parallel to the cross-like lines of the secondsmall opening holes 68B2, one each of third small opening holes 68B3 ofa smaller opening area than that of the second small opening hole 68B2is provided on the outer side of the second small opening holes 68B2.That is, the third small opening holes 68B3 are disposed in the fourcorners of the bottom face of the large opening hole 68A.

Further, those small opening holes 68B are designed to be able tocorrespond to the nine intersections X for forming the hollow material 4having the sectional view with a lattice form, and sixteen innerformation pieces 63B are provided in the lower part of the mandrel 63 tobe able to form the intersections X.

In the nine regions where one corner each of flange sections 63F of thesixteen inner formation pieces 63B gathers, the positions of each of theintersection points P correspond to the intersections X1, X2, and X3,respectively. Further, the positions of each of the small opening holes68B1, 68B2, and 68B3 are set so that the positions of the nineintersection points P and the centers of each of the small opening holes68B1, 68B2, and 68B3 of the nine billet guide holes 68 become consistentwith each other.

Further, the size of each of the inner formation pieces 63B issubstantially the same as the size of each of the inner formation pieces53B of the extrusion die 15 of the sixth embodiment.

Each of the sixteen inner formation pieces 63B is in the same squareshape, and disposed in an equivalent manner to form a square shape as awhole as shown in FIG. 23.

Note here that each of the inner formation pieces 63B is disposed withdifferent spaces provided with each other. That is, four each of thesixteen inner formation pieces 63B are disposed by sandwiching across-like gap L3, and the four each of the inner formation pieces 63Bare disposed by sandwiching a cross-like gap L4.

Among the sixteen inner formation pieces 63B, the side faces of theoutermost twelve inner formation pieces 63B oppose to the outerformation die 130B formed in the female-type member 130 with the gap L1provided therebetween.

Note here that the gap space of the gap L4 is designed to be a largerwidth gap space than the gap space of the gap L3, while the gap L1 isset to be the gap space that is between the gap L4 and the gap L3.Further, the material formation inner hole 52 is formed by the gap L3,the material formation inner hole 53 is formed by the gap L4, and thematerial formation outer hole 50 is formed by the gap L1.

Furthermore, those sixteen inner formation pieces 63B are to be insertedinto the outer formation die hole 130B of the female-type member 130.

Next, the hollow material 4 molded by the extrusion die 16 of theabove-described seventh embodiment will be described by referring toFIG. 24.

The hollow material 4 is formed in a lattice-form sectional shape, andconstituted with outer circumferential wall 4 a, 4 a in a squarecolumnar sectional shape, cross-like first partition walls 4 b 1, 4 b 1continuing from the outer circumferential walls 4 a, 4 a, and cross-likesecond partition walls 4 b 2, 4 b 2 provided in the center part in thelength direction of the first partition walls 4 b 1, 4 b 1.

Further, the first partition walls 4 b 1, 4 b 1 are formed to be thickercompared to the second partition walls 4 b 2, 4 b 2.

Furthermore, the part where the first partition walls 4 b 1 and 4 b 1intersect with each other is the intersection X in the greatestthickness, and the part where the first partition wall 4 b 1 and thesecond partition wall 4 b 2 intersect with each other is theintersection X2 that is in the second greatest thickness. Further, thepart where the second partition walls 4 b 2 and 4 b 2 intersect witheach other is the intersection X3 that is in the smallest thickness.

As shown in FIGS. 21 and 23, the first small opening hole 68B1corresponds to the thickest intersection X1, the second small openinghole 68B2 corresponds to the second thickest intersection X2, and thethird small opening hole 68B3 corresponds to the thinnest intersectionX3.

As a result, it becomes possible to form intersections of arbitrarythicknesses through changing the diameters of each of the small openingholes 68B1, 68B2, and 68B3.

With the extrusion die 16 of the seventh embodiment described above, itis also possible to acquire substantially the same actions as those ofthe extrusion die 15 of the sixth embodiment and substantially the sameeffects as those described in (1), (2), (6), (7), and (9). In addition,it is possible to achieve the following effect:

(10) The large opening hole 68A to the small opening holes 68B of thebillet guide hole 68 are constituted with three kinds of the holes withdifferent diameters, i.e., the first small opening hole 68B1, the secondsmall opening hole 68B2, and the third small opening hole 68B3. Each ofthose corresponds to the intersections of different thicknesses, i.e.,the intersection X1 where the first partition walls 4 b 1 and 4 b 1intersect, the intersection X2 where the first partition wall 4 b 1 andthe second partition wall 4 b 2 intersect, and the third intersection X3where the second partition walls 4 b 2 and 4 b 2 intersect. Therefore,the hollow material 4 in a lattice-form sectional shape having thepartition walls of different thicknesses can be molded easily.

Next, eighth to tenth embodiments of the extrusion die of the presentinvention will be described by referring to FIGS. 25 and 26.

In the first to seventh embodiments, the hollow materials 1 to 6 moldedby each of the extrusion dice 10 to 16 have complicated sectional shapeswith the intersections X formed by the partition walls 1 b and the like.However, the hollow materials are not limited to such cases. Withextrusion dice 17 to 19 of the eighth to tenth embodiments of thepresent invention, it is possible to mold hollow materials 7, 8, and 9having curve-shaped partition walls 7 b, 8 b, and 9 b inside thereof asshown in FIGS. 25A, 25B and FIG. 26, through changing the shapes of theinner formation pieces, respectively.

That is, as shown in FIG. 25A, the hollow material 7 molded by theextrusion die 17 of the eighth embodiment is constituted with: outercircumferential walls 7 a, 7 a in a square sectional shape; andcurve-shaped partition walls 7 b, 7 b provided inside those outercircumferential walls 7 a, 7 a. Those partition walls 7 b, 7 b areformed to connect the center parts in the length direction of theorthogonal outer circumferential walls 7 a, 7 a with curve-shaped lines.

The partition walls 7 b and 7 b are constituted with a single innerformation piece 73B1 and two inner formation pieces 73B2 disposed bysandwiching the inner formation piece 73B1. Those inner formation piece73B1 and the inner formation pieces 73B2 are designed to be insertedinto the outer formation die hole 30B formed in the female-type member30.

Note here that the material formation outer hole 51 of the gap L1 isformed between each of the inner formation piece 7381, the innerformation piece 73B2, and the outer formation die hole 30B. Further, thethickness of the partition walls 7 b and 7 b is set to be the gap L2,and the material formation inner hole 51 is formed by the gap L2.

At the part where the curved sections of the partition walls 7 b and 7 bcome closest to each other, the small openings 78B and 78B of the billetguide hole 78 are disposed opposing to each other. The large openinghole 28A of the billet guide hole 78 is connected to those smallopenings 78B and 78B.

Note that the billet guide hole 78 is provided in the center part of themandrel, not shown. Further, the entire structure of the extrusion die17 is substantially the same as the entire structure of the extrusiondie 10 and the like of the first embodiment.

With the structure described above, the billet is fed from the upstreamside, a part thereof is introduced into the large opening hole 78A ofthe billet guide 78, and extruded out from the gap between the innerformation piece 73B1 and the inner formation pieces 73B2 via the smallopenings 78B, 78B. At that time, the billet introduced into the smallopenings 78B, 78B is extruded out from the material formation inner hole51. Therefore, the curved-shape partition walls 7 b and 7 b can beformed easily.

Next, the extrusion die 18 of the ninth embodiment will be described.

As shown in FIG. 25B, the hollow material 8 molded by the extrusion die18 is constituted with: outer circumferential walls 8 a, 8 a in a squaresectional shape; and curve-shaped partition walls 8 b, 8 b providedinside those outer circumferential walls 8 a, 8 a. Each of thosepartition walls 8 b and 8 b is formed in a curved shape projected towardthe center part of the sectional shape of the hollow material 8 from theopposing outer circumferential walls 8 a and 8 a.

The partition walls 8 b and 8 b are constituted with a single innerformation piece 83B1 and two inner formation pieces 83B2 disposed bysandwiching the inner formation piece 83B1. Those inner formation piece83B1 and the inner formation pieces 83B2 are designed to be insertedinto the outer formation die hole 30B formed in the female-type member30.

Note here that the material formation outer hole 50 of the gap L1 isformed between each of the inner formation piece 83B1, the innerformation piece 83B2, and the outer formation die hole 30B. Further, thethickness of the partition walls 8 b and 8 b is set to be the gap L2,and the material formation inner hole 51 is formed by the gap L2.

Further, at the part where the curved sections of the partition walls 8b and 8 b come closest to each other, the small openings 88B and 88B ofthe billet guide hole 88 are disposed opposing to each other. The largeopening hole 88A of the billet guide hole 88 is connected to those smallopenings 88B and 88B.

Note that the billet guide hole 88 is provided in the center part of themandrel, not shown. Further, the entire structure of the extrusion die18 is substantially the same as the entire structure of the extrusiondie 10 and the like of the first embodiment.

With the structure described above, the billet is fed from the upstreamside, a part thereof is introduced into the large opening hole 88A ofthe billet guide 88, and extruded out from the gaps between the innerformation piece 83B 1 and the inner formation pieces 83B2 via the smallopenings 88B, 88B.

At that time, the billet introduced into the small openings 88B, 88B isextruded out from the material formation inner hole 51. Therefore, thecurve-shaped partition walls 8 b and 8 b can be formed easily.

Next, the extrusion die 19 of the tenth embodiment will be described.

As shown in FIG. 26, the hollow material 9 molded by the extrusion die19 is constituted with: outer circumferential walls 9 a, 9 a in a squaresectional shape; and wave-shaped partition walls 9 b, 9 b providedinside those outer circumferential walls 9 a, 9 a. Each of thosepartition walls 9 b and 9 b is formed in a wave-like shape connectingbetween the opposing outer circumferential walls 9 a and 9 a.

The partition walls 9 b and 9 b are constituted with a single innerformation piece 93B1 and two inner formation pieces 93B2 disposed bysandwiching the inner formation piece 93B1. Those inner formation piece93B1 and the inner formation pieces 93B2 are designed to be insertedinto the outer formation die hole 30B formed in the female-type member30.

Note here that the material formation outer hole 50 of the gap L1 isformed between each of the inner formation piece 93B1, the innerformation piece 93B2, and the outer formation die hole 30B. Further, thethickness of the partition walls 9 b and 9 b is set to be the gap L2,and the material formation inner hole 51 is formed by the gap L2.

Further, at substantially the center parts in the respective lengthdirections of the partition walls 9 b and 9 b, the small openings 98Band 98B of the billet guide hole 98 are disposed opposing to each other.The large opening hole 98A of the billet guide hole 98 is connected tothose small openings 98B and 98B.

Note that the billet guide hole 98 is provided in the center part of themandrel, not shown. Further, the entire structure of the extrusion die19 is substantially the same as the entire structure of the extrusiondie 10 and the like of the first embodiment.

With the structure described above, the billet is fed from the upstreamside, a part thereof is introduced into the large opening hole 98A ofthe billet guide 98, and extruded out from the gaps between the innerformation piece 93B 1 and the inner formation pieces 93B2 via the smallopenings 98B, 98B.

At that time, the billet introduced into the small openings 98B, 98B isextruded out from the material formation inner hole 51. Therefore, thecurve-shaped partition walls 9 b and 9 b can be formed easily.

While the present invention has been described above by referring to theembodiments, the present invention is not limited only to theembodiments. Various changes and modifications occurred to those skilledin the art can be applied to the structures and details of the presentinvention. Further, the present invention also includes mutual andproper combinations of a part of or a whole of each of the embodiments.

For example, in the fifth embodiment, the large opening hole 48A of thebillet guide hole 48 of the extrusion die 14 is formed substantially ina square shape on a plan shape and in a dented recessed shape toward thedownstream side. However, as shown in FIG. 27, the large opening hole78A in the extrusion die 14A of a modification example is formed as atapered-shape hole that becomes narrower from the top face of themandrel section 43 toward the bottom face of the large opening hole 78A.

Further, the large opening holes 58A and 68A of the billet guide holes58 and 68 of the sixth and seventh embodiments may also be formed as atapered-shape hole that becomes narrower from the top face of themandrel sections 53 and 63 toward the bottom face of the large openingholes 58A and 68A as in the above case.

Further, while the billet guide hole 28 is formed as a two-stagestructure of the large opening hole 28A and the small opening hole 28Band the bottom face of the large opening hole 28A is formed as a flatface in the first and third embodiments, the structure thereof is notlimited to such case. The bottom face of the large opening hole 28A maybe formed as a bottom face constituted with an angular part with asloping face of 45°, for example. With this, flow of the billet B canbecome still smoother.

Further, while each of the extrusion dice 10 to 13 of the first tofourth embodiments can mold the hollow material 1 having a sectionalshape with a cross inside thereof and each of the extrusion dice 14 to16 of the fifth to seventh embodiments can mold the hollow materials 2to 4 having a sectional shape with a lattice form inside thereof, thestructures are not limited only to such cases. For example, as shown inFIG. 28A, it is possible to employ a structure capable of molding thehollow material 5 in which two intersections X are formed laterally withtwo vertically disposed outer circumferential walls 5 a, 5 a and asingle laterally disposed partition walls 5 b, 5 b through changing theshapes of a plurality of inner formation pieces.

Further, as shown in FIG. 28B, it is also possible to employ a structurecapable of forming the hollow material 6 having an external shape inwhich partition walls 6 c, 6 c are provided in an X-letter form at thefour corners of the external circumferential walls 6 a, 6 a formed in asquare columnar shape through changing the shapes of a plurality ofinner formation pieces.

INDUSTRIAL APPLICABILITY

The extrusion die of the present invention is utilized when moldinghollow materials having partition walls inside thereof by using ahigh-strength alloy, particularly a high-strength aluminum alloy such asthe so-called 7000 series.

REFERENCE NUMERALS

-   -   1 Hollow material having sectional shape with cross inside        (hollow material formed by first to fourth embodiment)    -   2 Hollow material having sectional shape with lattice inside        (hollow material formed by fifth embodiment)    -   3 Hollow material having sectional shape with lattice inside        (hollow material formed by sixth embodiment)    -   4 Hollow material having sectional shape with lattice inside        (hollow material formed by seventh embodiment)    -   10 Extrusion die for forming hollow material (first embodiment)    -   11 Extrusion die for forming hollow material (second embodiment)    -   12 Extrusion die for forming hollow material (third embodiment)    -   13 Extrusion die for forming hollow material (fourth embodiment)    -   14 Extrusion die for forming hollow material (fifth embodiment)    -   15 Extrusion die for forming hollow material (sixth embodiment)    -   16 Extrusion die for forming hollow material (seventh        embodiment)    -   20 Male-type member    -   22 Spider    -   23 Mandrel section    -   23B Inner formation piece    -   24 Bridge section    -   24 a to 24 d First to fourth bridges    -   24A Bridge tip outer circumferential face    -   25 Holder section    -   26 Bridge holding section    -   26B Bridge receiving face as bridge abutting/engaging face    -   30 Female-type member    -   30B Outer formation die hole    -   50 Material formation outer hole    -   51 Material formation inner hole    -   BH Billet insertion hole (billet merging space)    -   BH1 Billet insertion hole (billet merging space)    -   S Billet introducing part    -   M Bridge section press-fit structure    -   N Bridge section shrink-fit structure

1. An extrusion die for forming a hollow material, comprising: amale-type member which forms an inner shape of the hollow material whileguiding a billet constituted with an aluminum alloy fed from an upstreamside toward a downstream side; and a female-type member which holds themale-type member with an outer circumferential part and forms an outershape of the hollow material, wherein: the male-type member comprises amandrel section for forming the inner shape, and a holder sectionconnected integrally to an outer circumferential part of the mandrelsection via a plurality of bridge sections; a billet guide hole forguiding a part of the billet toward the downstream side is provided in acenter region of the mandrel section; an upstream-side opening area ofthe billet guide hole is formed larger than a downstream-side openingarea; and a plurality of inner formation pieces are fixedly mounted on adownstream side of the billet guide hole and at positions for formingcontinuous partition walls inside the hollow material while keeping abillet flow-in gap space forming a merging space of the billet flowingin from each of the bridge sections toward the downstream side.
 2. Theextrusion die for forming the hollow material as claimed in claim 1,wherein the billet guide hole is formed as a stepped hole constitutedwith an upstream-side large opening hole and a downstream-side smallopening hole formed in the bottom part of the large opening hole.
 3. Theextrusion die for forming the hollow material as claimed in claim 2,wherein an inner wall face of the upstream-side large opening hole isformed in a tapered shape in which an opening side has a larger openingarea than a bottom part of the large opening hole.
 4. The extrusion diefor forming the hollow material as claimed in claim 1, wherein thebillet guide hole is formed in a tapered shape narrowed from theupstream-side opening toward the downstream-side opening.
 5. Theextrusion die for forming the hollow material as claimed in claim 2,wherein a plurality of the downstream-side small opening holes areprovided.
 6. (canceled)
 7. The extrusion die for forming the hollowmaterial as claimed in claim 3, wherein a plurality of thedownstream-side small opening holes are provided.
 8. The extrusion diefor forming the hollow material as claimed in claim 5, wherein the smallopening holes of the billet guide hole are disposed by opposing tointersection points of gaps for forming a plurality of partition wallsset by the plurality of inner formation pieces.
 9. The extrusion die forforming the hollow material as claimed in claim 7, wherein the smallopening holes of the billet guide hole are disposed by opposing tointersection points of gaps for forming a plurality of partition wallsset by the plurality of inner formation pieces.